JP4661305B2 - Hot metal decarburization refining method - Google Patents
Hot metal decarburization refining method Download PDFInfo
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- JP4661305B2 JP4661305B2 JP2005093415A JP2005093415A JP4661305B2 JP 4661305 B2 JP4661305 B2 JP 4661305B2 JP 2005093415 A JP2005093415 A JP 2005093415A JP 2005093415 A JP2005093415 A JP 2005093415A JP 4661305 B2 JP4661305 B2 JP 4661305B2
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- 229910052751 metal Inorganic materials 0.000 title claims description 87
- 239000002184 metal Substances 0.000 title claims description 87
- 238000007670 refining Methods 0.000 title claims description 52
- 238000005261 decarburization Methods 0.000 title claims description 44
- 238000000034 method Methods 0.000 title claims description 34
- 239000002893 slag Substances 0.000 claims description 104
- 229910000831 Steel Inorganic materials 0.000 claims description 76
- 239000010959 steel Substances 0.000 claims description 76
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 53
- 239000002826 coolant Substances 0.000 claims description 32
- 229910052742 iron Inorganic materials 0.000 claims description 26
- 238000006477 desulfuration reaction Methods 0.000 claims description 19
- 230000023556 desulfurization Effects 0.000 claims description 19
- 238000007664 blowing Methods 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 238000009749 continuous casting Methods 0.000 claims description 3
- 238000009628 steelmaking Methods 0.000 claims description 3
- 238000007885 magnetic separation Methods 0.000 description 42
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 30
- 229910052698 phosphorus Inorganic materials 0.000 description 30
- 239000011574 phosphorus Substances 0.000 description 30
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 27
- 229910052717 sulfur Inorganic materials 0.000 description 27
- 239000011593 sulfur Substances 0.000 description 27
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 25
- 239000002699 waste material Substances 0.000 description 21
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 18
- 235000013980 iron oxide Nutrition 0.000 description 13
- 235000012255 calcium oxide Nutrition 0.000 description 9
- 239000000292 calcium oxide Substances 0.000 description 9
- 238000001816 cooling Methods 0.000 description 9
- 239000002994 raw material Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 239000002436 steel type Substances 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000007790 scraping Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- -1 iron ore Chemical class 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 239000010813 municipal solid waste Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Processing Of Solid Wastes (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
Description
本発明は、転炉における溶銑の脱炭精錬方法に関し、詳しくは、スラグから回収した磁選屑を冷却材として利用した、溶銑の脱炭精錬方法に関するものである。 The present invention relates to a method for decarburizing and refining hot metal in a converter, and more particularly to a method for decarburizing and refining hot metal using magnetically separated scrap recovered from slag as a coolant.
溶銑を脱炭精錬して溶鋼を溶製する、転炉における溶銑の脱炭精錬では、主原料を溶銑と鉄スクラップとし、この溶銑の有する顕熱と、溶銑中に含まれる炭素や珪素の酸化による発熱とを熱源として、次工程の要求する溶鋼温度を確保している。そして、主原料中の溶銑の比率（「溶銑配合率」という）を、生産量の変動や鉄スクラップ価格の変動などから常時最適条件となるように変動させている。また、この脱炭精錬では、主原料の他に副原料として、生石灰、ドロマイト、蛍石などの造滓材と、鉄鉱石、ミルスケール、製鉄ダストなどの精錬終了時点の溶鋼温度調整用の冷却材と、更に、成分調整用の合金鉄と、を使用している。溶銑配合率によって溶鋼温度のおおよその値は決定されるが、冷却材を使用することにより、精度の良い温度調整が可能となる。 In the decarburization and refining of hot metal in a converter, where the hot metal is decarburized and refined, the main raw materials are hot metal and iron scrap. The sensible heat of this hot metal and the oxidation of carbon and silicon contained in the hot metal The temperature of the molten steel required in the next process is secured using the heat generated by Then, the ratio of hot metal in the main raw material (referred to as “hot metal mixture ratio”) is constantly changed so as to be in an optimum condition due to fluctuations in production volume and iron scrap price. In addition, in this decarburization refining, as an auxiliary material in addition to the main raw material, as a raw material such as quick lime, dolomite and fluorite, cooling for adjusting the temperature of molten steel at the end of refining such as iron ore, mill scale and iron dust The material and, further, alloy iron for component adjustment are used. Although the approximate value of the molten steel temperature is determined by the hot metal content, the temperature can be adjusted with high accuracy by using a coolant.
ところで、最近、溶銑から溶鋼を溶製する際、溶銑を転炉で脱炭精錬する前に、溶銑段階で脱硫処理及び脱燐処理を予め実施（これらを「溶銑予備処理」という）し、この溶銑を転炉で脱炭精錬して溶鋼を溶製する方法が主流となってきている。また、脱燐処理を効率的に行うために脱燐処理に先立って溶銑の脱珪処理を行う場合もある。この脱珪処理も溶銑予備処理の１つである。 By the way, recently, when molten steel is made from hot metal, desulfurization treatment and dephosphorization treatment are carried out in advance in the hot metal stage before decarburizing and refining the hot metal in a converter (these are called “hot metal pretreatment”). A method of melting molten steel by decarburizing and refining hot metal in a converter has become the mainstream. In addition, in order to efficiently perform the dephosphorization process, there is a case where the hot metal desiliconization process is performed prior to the dephosphorization process. This desiliconization process is also one of the hot metal preliminary processes.
この脱硫処理、脱燐処理及び脱珪処理を施した後には、それぞれ除去対象成分（硫黄、燐、珪素）を濃縮したスラグが発生する。前工程の除去対象成分が、後工程において溶銑へピックアップすることを防止するために、前工程の終了後には生成したスラグは溶銑を収容した処理容器から除去される。スラグの除去方法には、掻き出し機（「スラグドラッガー」とも呼ぶ）を用いて掻き出す方法、或いはスラグを真空吸引する方法などがあるが、何れの方法であってもスラグのみを排出することは困難であり、排出されたスラグには１０〜３０質量％程度の地金分が混入する。また、当然ながら、転炉での脱炭精錬終了後にも地金を混入したスラグが発生する。また更に、転炉から出鋼された溶鋼を受鋼した取鍋からも地金を混入したスラグが発生する。 After performing this desulfurization process, dephosphorization process, and desiliconization process, the slag which each concentrated the removal object component (sulfur, phosphorus, silicon) generate | occur | produces. In order to prevent the component to be removed in the previous step from being picked up to the molten iron in the subsequent step, the generated slag is removed from the processing container containing the molten iron after the completion of the previous step. Slag removal methods include scraping using a scraping machine (also called “slag dragger”) or vacuum suction of slag, but it is difficult to discharge only slag by either method. In the discharged slag, about 10 to 30% by mass of the metal is mixed. Of course, slag mixed with metal is generated after decarburization refining in the converter. Furthermore, slag mixed with metal is also generated from a ladle that receives the molten steel produced from the converter.
そのため、これらのスラグは冷却後に破砕され、破砕されたスラグを磁力選別することで地金が回収されている。このようにして回収した地金を「磁選屑」と称している。但し、破砕し且つ磁力選別したとはいえども、スラグと地金とが完全に分離されることはなく、回収される磁選屑には、３０〜８０質量％のスラグが付着している。 Therefore, these slags are crushed after cooling, and the bullion is recovered by magnetically sorting the slags that have been crushed. The bullion collected in this way is referred to as “magnetically separated waste”. However, although crushed and magnetically sorted, the slag and the metal are not completely separated, and 30 to 80% by mass of slag is attached to the collected magnetic waste.
回収した磁選屑は、鉄源として再溶解されてリサイクル使用される。例えば、特許文献１には、転炉における溶銑の脱炭精錬時の冷却材として磁選屑を使用することが開示されており、また特許文献２には、溶銑の脱燐処理または溶銑の脱炭精錬で発生したスラグから回収した磁選屑を、転炉型精錬容器における溶銑の脱燐処理で再溶解して利用する方法が開示されている。
磁選屑には、処理工程に応じて、それぞれ除去対象成分を濃縮したスラグが付着する。つまり、溶銑の脱硫処理で生成するスラグから回収した磁選屑の付着スラグの硫黄含有量は高く、同様に、溶銑の脱燐処理で生成するスラグから回収した磁選屑に付着するスラグの燐含有量は高くなる。 The slag which concentrated each removal object component adheres to magnetic separation waste according to a process. That is, the sulfur content of the magnetic slag collected from the slag produced by the desulfurization treatment of the hot metal is high, and similarly, the phosphorus content of the slag adhered to the magnetic sewage collected from the slag produced by the dephosphorization treatment of the hot metal. Becomes higher.
従って、回収した磁選屑を転炉での溶銑の脱炭精錬における冷却材として使用すると、磁選屑に付着したスラグに起因して、脱炭精錬後の溶鋼中の燐濃度または硫黄濃度が上昇する。これを防止するには、脱炭精錬において生石灰などの造滓剤の使用量を増やす必要があり、製造コストの上昇をもたらす。脱炭精錬後の溶鋼中の燐、硫黄が上昇しない程度だけ使用すれば問題はないが、その場合には発生する地金を消費することができない。 Therefore, when the recovered magnetic separation scrap is used as a coolant in the decarburization refining of hot metal in the converter, the phosphorus concentration or sulfur concentration in the molten steel after decarburization refining increases due to the slag adhering to the magnetic separation waste. . In order to prevent this, it is necessary to increase the amount of a fouling agent such as quick lime used in decarburization refining, resulting in an increase in production cost. There is no problem if it is used only to such an extent that phosphorus and sulfur in the molten steel after decarburization refining does not rise, but in that case, the generated metal cannot be consumed.
本発明は上記事情に鑑みてなされたもので、その目的とするところは、転炉での溶銑の脱炭精錬において、磁選屑の使用量を制限しなくても、また、生石灰などの造滓剤の使用量を増やさなくても、溶鋼中の燐濃度及び硫黄濃度の上昇を起こすことなく、磁選屑を冷却材として使用することのできる、溶銑の脱炭精錬方法を提供することである。 The present invention has been made in view of the above circumstances, and the object of the present invention is not to limit the amount of magnetic separation scrap used in the decarburization and refining of hot metal in a converter, but also to produce lime such as quick lime. It is an object of the present invention to provide a hot metal decarburizing and refining method capable of using magnetically separated scrap as a coolant without increasing the phosphorus concentration and sulfur concentration in molten steel without increasing the amount of the agent used.
上記課題を解決するための第１の発明に係る溶銑の脱炭精錬方法は、高炉で製造された溶銑に対して脱硫処理及び脱燐処理を行う、溶銑の予備処理工程と、脱硫処理及び脱燐処理が施された溶銑を転炉で脱炭精錬して溶鋼を製造する転炉脱炭精錬工程と、転炉脱炭精錬によって製造された溶鋼を連続鋳造する鋳造工程と、を備えた溶銑・溶鋼の処理工程で発生するスラグを、溶銑系スラグと溶鋼系スラグとに分別して回収し、回収した溶鋼系スラグを破砕し、破砕後に磁力選別して回収した、スラグの付着する磁選屑を、脱硫処理及び脱燐処理が施された溶銑の転炉での脱炭精錬の吹錬２０〜３０％の時点から吹錬中期の時点まで冷却材として投入添加し、その後、吹錬７５〜９０％の時点でサブランスを投入し、サブランスの投入によって測定された浴温度及び溶銑中炭素濃度から推定される必要冷却材量に基づいて、前記磁選屑を冷却材として吹錬末期にも投入添加することを特徴とするものである。 A hot metal decarburizing and refining method according to a first aspect of the present invention for solving the above-described problem includes a hot metal pretreatment process, a desulfurization process and a desulfurization process for performing desulfurization treatment and dephosphorization treatment on hot metal produced in a blast furnace. A hot metal process comprising: a converter decarburization refining process for producing molten steel by decarburizing and refining hot metal treated with phosphorous in a converter; and a casting process for continuously casting the molten steel produced by converter decarburizing refining. the slug generated in molten steel treatment process, and collected separately to the hot metal slag and the molten steel slag, disrupting the collected molten steel slag were recovered by magnetic separation after crushing, the magnetic separation debris adhering slag , Desulfurization treatment and dephosphorization treatment of hot metal converter in the decarburization refining blowing 20-30% as a coolant from the time point to the middle of the blowing, and then blown 75-90 % At the time of% Based on the required coolant amount estimated from the constant has been bath temperature and hot metal in the carbon concentration, is characterized in that also put added blow end of the magnetic separation scrap as a coolant.
第２の発明に係る溶銑の脱炭精錬方法は、第１の発明において、前記磁選屑は、直径が５〜７０ｍｍであることを特徴とするものである。 The hot metal decarburizing and refining method according to the second invention is characterized in that, in the first invention, the magnetically separated scrap has a diameter of 5 to 70 mm.
本発明によれば、溶銑の脱硫処理及び脱燐処理などで発生する溶銑系スラグと、溶銑の転炉脱炭精錬及び溶鋼を収容した取鍋などから発生する溶鋼スラグとに分別して回収し、このようにして回収した溶鋼スラグから回収される磁選屑を脱炭精錬における冷却材として使用するので、磁選屑に付着するスラグからの溶鋼への燐及び硫黄のピックアップを防止することができる。また、冷却材として一般的に使用される鉄鉱石などの酸化鉄と異なり、磁選屑は酸化鉄を含有していないので、顕熱及び潜熱のみから温度降下量を予測することができ、溶銑及び溶鋼の温度調整が容易となる。また更に、密度が大きいことから溶融スラグ中に埋没し、溶銑或いは溶鋼の温度変化が迅速に現われ、温度調整の精度を高めることができる。 According to the present invention, the molten iron slag generated in the hot metal desulfurization treatment and the dephosphorization treatment, and the molten steel slag generated from the ladle containing the molten steel converter decarburization refining and molten steel, and recovered, Since the magnetic separation scrap recovered from the molten steel slag recovered in this way is used as a coolant in decarburization refining, pick-up of phosphorus and sulfur from the slag adhering to the magnetic separation scrap to the molten steel can be prevented. Also, unlike iron oxides such as iron ore, which are commonly used as coolants, magnetic separation scraps do not contain iron oxide, so the temperature drop can be predicted from only sensible heat and latent heat, Temperature adjustment of molten steel becomes easy. Furthermore, since the density is high, it is buried in the molten slag, and the temperature change of the hot metal or molten steel appears rapidly, and the accuracy of temperature adjustment can be increased.
以下、本発明を具体的に説明する。 The present invention will be specifically described below.
本発明では、高炉などで製造された溶銑の転炉における脱炭精錬において、溶鋼系スラグから回収した磁選屑を冷却材として精錬中に転炉炉口から転炉内に投入して使用する。使用する転炉は、上吹き転炉、底吹き転炉、上底吹き転炉など、どのような型式であっても構わない。脱炭精錬に使用する溶銑は、脱燐処理や脱硫処理などの溶銑予備処理が施されていても、また、溶銑予備処理が施されていなくても、どちらであってもよい。但し、脱炭精錬では、溶製される溶鋼の燐含有量を所望する範囲に調整するために、使用する溶銑の燐レベルに応じて、生石灰などの造滓材の添加量は変更する必要がある。 In the present invention, in decarburization refining in a hot metal converter manufactured in a blast furnace or the like, magnetically separated scrap recovered from molten steel slag is used as a coolant by being charged into the converter from the converter furnace port during refining. The converter to be used may be of any type such as a top blowing converter, a bottom blowing converter, and a top bottom blowing converter. The hot metal used for decarburization refining may be either hot metal pretreatment such as dephosphorization treatment or desulfurization treatment, or no hot metal pretreatment. However, in decarburization refining, in order to adjust the phosphorus content of the molten steel to the desired range, it is necessary to change the addition amount of the slagging material such as quick lime according to the phosphorus level of the hot metal used. is there.
高炉などで製造された溶銑をトーピードカーや取鍋型の溶銑鍋で受銑した以降、この溶銑に転炉において脱炭精錬を施して溶鋼を溶製し、更に、この溶鋼を連続鋳造機で連続鋳造するまでの溶銑・溶鋼の処理工程においては種々のスラグが発生する。具体的には、溶銑予備処理の脱珪処理により発生するスラグ、溶銑予備処理の脱燐処理により発生するスラグ、溶銑予備処理の脱硫処理により発生するスラグ、溶銑の転炉脱炭精錬により発生するスラグ、転炉で溶製された溶鋼を受鋼した取鍋から発生するスラグ、連続鋳造機のタンディッシュから発生するスラグなどが挙げられる。尚、高炉から出銑される溶銑の化学成分組成は、炭素が４〜５質量％、珪素が０．２〜０．５質量％、燐が０．９〜０．１４質量％、硫黄が０．０３〜０．０５質量％程度であり、鋼の材質特性上からみて不純物元素である燐及び硫黄の含有量が高い。 After receiving the hot metal produced in a blast furnace etc. in a torpedo car or ladle type hot metal ladle, this hot metal is decarburized and refined in a converter to melt the molten steel. Various slag is generated in the hot metal / molten steel treatment process until casting. Specifically, slag generated by desiliconization of hot metal pretreatment, slag generated by dephosphorization of hot metal pretreatment, slag generated by desulfurization of hot metal pretreatment, generated by converter decarburization and refining of hot metal Examples include slag, slag generated from a ladle that has received molten steel melted in a converter, and slag generated from a tundish of a continuous casting machine. The chemical composition of the hot metal discharged from the blast furnace is 4-5 mass% for carbon, 0.2-0.5 mass% for silicon, 0.9-0.14 mass% for phosphorus, and 0 for sulfur. 0.03 to 0.05% by mass, and the content of phosphorus and sulfur as impurity elements is high in view of the material properties of steel.
本発明においては、これらのスラグを溶銑系スラグと溶鋼系スラグの２つに大別する。溶銑系スラグとは、溶銑予備処理の脱珪処理により発生するスラグ（「脱珪スラグ」と呼ぶ）、溶銑予備処理の脱燐処理により発生するスラグ（「脱燐スラグ」と呼ぶ）、及び溶銑予備処理の脱硫処理により発生するスラグ（「脱硫スラグ」と呼ぶ）であり、脱珪スラグは珪素含有量が高く、脱燐スラグは燐含有量が高く、脱硫スラグは硫黄含有量が高いという特徴を有する。また、スラグに混入する地金自体も、燐または硫黄の含有量が高いという特徴がある。例えば、脱珪スラグに混入する地金は燐及び硫黄が高く、脱燐スラグ及び脱硫スラグでは、処理工程の順序に応じて何れかのスラグに混入する地金の燐または硫黄が高くなる。 In the present invention, these slags are roughly divided into two types, hot metal slag and molten steel slag. Hot metal-based slag refers to slag generated by desiliconization in hot metal pretreatment (referred to as “desiliconized slag”), slag generated by dephosphorization in hot metal pretreatment (referred to as “dephosphorized slag”), and hot metal Slag generated by pre-treatment desulfurization (referred to as “desulfurization slag”). Desiliconization slag has a high silicon content, dephosphorization slag has a high phosphorus content, and desulfurization slag has a high sulfur content. Have In addition, the metal itself mixed in the slag is characterized by high phosphorus or sulfur content. For example, bullion mixed in desiliconized slag is high in phosphorus and sulfur, and in dephosphorized slag and desulfurized slag, phosphorus or sulfur contained in any slag is high depending on the order of processing steps.
一方、溶鋼系スラグとは、溶銑の転炉脱炭精錬により発生するスラグ（「転炉脱炭スラグ」と呼ぶ）、転炉で溶製された溶鋼を受鋼した取鍋から発生するスラグ（「取鍋スラグ」と呼ぶ）、連続鋳造機のタンディッシュから発生するスラグ（「タンディッシュスラグ」と呼ぶ）であり、これらのスラグの燐含有量及び硫黄含有量は、溶銑系スラグに比べて十分に低い。 On the other hand, molten steel slag refers to slag generated by decarburization and refining of molten iron (referred to as “converter decarburization slag”), slag generated from a ladle receiving molten steel melted in the converter ( "Ladle slag"), slag generated from the tundish of continuous casting machines (called "tundish slag"), the phosphorus content and sulfur content of these slags compared to hot metal slag Low enough.
つまり、溶銑の転炉脱炭精錬の前には、脱燐処理及び脱硫処理が施されているので、転炉脱炭スラグの燐含有量及び硫黄含有量は低くなる。仮に、転炉脱炭精錬の前に脱燐処理及び脱硫処理が施されていない場合にも、使用する溶銑の燐含有量に応じて、転炉脱炭精錬では脱燐及び脱硫のために多量の石灰系造滓材を使用する必要があり、結局、スラグ中の燐及び硫黄は希釈され、転炉脱炭スラグの燐及び硫黄の含有量は低くなる。 That is, since dephosphorization treatment and desulfurization treatment are performed before converter decarburization refining of hot metal, the phosphorus content and sulfur content of the converter decarburization slag become low. Even if dephosphorization treatment and desulfurization treatment are not performed before converter decarburization refining, converter decarburization refining requires a large amount for dephosphorization and desulfurization depending on the phosphorus content of the hot metal used. Therefore, the phosphorus and sulfur in the slag are diluted, and the phosphorus and sulfur contents of the converter decarburization slag are lowered.
取鍋スラグは、溶鋼を転炉から取鍋に出湯する際に溶鋼に混じって流出した転炉脱炭スラグを主体とするスラグであり、また、このスラグに、ＣａＯ／Ａｌ2 Ｏ3 の調整のために生石灰と、酸素ポテンシャル調整のための金属アルミニウムとが添加されたスラグもある。何れの取鍋スラグも、燐及び硫黄の含有量は低い。取鍋スラグでは、金属アルミニウムはＡｌ2Ｏ3 の形態になっている。 The ladle slag is a slag mainly composed of converter decarburization slag that flows out of the molten steel when it is poured from the converter to the ladle. In addition, this slag is adjusted with CaO / Al 2 O 3 . There is also a slag to which quick lime and metallic aluminum for adjusting the oxygen potential are added. Any ladle slag has a low phosphorus and sulfur content. In the ladle slag, the metallic aluminum is in the form of Al 2 O 3 .
タンディッシュスラグは、鋳造末期に溶鋼に混じって取鍋スラグがタンディッシュに流出したもの、或いは、タンディッシュ内溶鋼の保温のためにタンディッシュに投入した合成フラックスを主体とするものであり、何れのタンディッシュスラグも燐及び硫黄の含有量は低い。また、転炉脱炭スラグ、取鍋スラグ及びタンディッシュスラグに混入する地金は、脱燐、脱硫、脱炭の各精錬が施されたものであり、燐及び硫黄の含有量は低い。 Tundish slag is mainly composed of ladle mixed with molten steel at the end of casting and ladle slag flowing into the tundish, or synthetic flux introduced into the tundish to keep the molten steel inside the tundish. The tundish slag also has a low phosphorus and sulfur content. In addition, the bullion mixed in the converter decarburization slag, ladle slag and tundish slag has been subjected to refining of dephosphorization, desulfurization, and decarburization, and the contents of phosphorus and sulfur are low.
本発明では、これらの溶鋼スラグを冷却水などによって冷却し、冷却された溶鋼系スラグを回収して破砕・分級し、その後、磁力選別して、溶銑の脱炭精錬で冷却材として使用する磁選屑を回収する。磁選屑には、付着スラグ分として３０〜８０質量％のスラグ分が含まれている。この磁選屑を再度破砕・分級し、その後再度磁力選別し、鉄分の含有量を高めた磁選屑であればより望ましい。 In the present invention, these molten steel slags are cooled with cooling water or the like, and the cooled molten steel slag is recovered, crushed and classified, and then magnetically selected to be used as a coolant in hot metal decarburization refining. Collect trash. The magnetic separation waste contains 30 to 80% by mass of slag as adhering slag. It is more desirable if the magnetic separation waste is crushed and classified again, and then magnetic separation is performed again to increase the iron content.
冷却材として使用する磁選屑のサイズは、５〜７０ｍｍとすることが好ましい。５ｍｍ未満であると、転炉炉口からの投入時、大量に発生する排ガスとともに排気ダクトに流されて、添加歩留まりが低下する。一方、上限の７０ｍｍは副原料投入設備の設備仕様によるもので、設備的に可能ならば、上限値を規定する必要はなく、幾らであっても構わない。但し、あまり大きくすると、スラグの分離が悪くなるので、７０ｍｍ程度が妥当である。尚、本発明におけるサイズとは、篩目のサイズで規定するもので、５〜７０ｍｍのサイズとは、目開き寸法が５ｍｍの篩を通過せず、目開き寸法が７０ｍｍの篩を通過するもので、長円形の場合には長径が７０ｍｍを超えても問題ない。 The size of the magnetic separation waste used as the coolant is preferably 5 to 70 mm. When it is less than 5 mm, when it is introduced from the converter furnace port, it is caused to flow through the exhaust duct together with a large amount of exhaust gas, and the addition yield is reduced. On the other hand, the upper limit of 70 mm is due to the equipment specifications of the auxiliary raw material charging equipment, and if it is possible in terms of equipment, there is no need to define the upper limit value, and it does not matter. However, if it is too large, the separation of slag becomes worse, so about 70 mm is appropriate. In addition, the size in this invention is prescribed | regulated by the size of a sieve mesh, and the size of 5-70 mm does not pass a sieve with an opening dimension of 5 mm, and passes a sieve with an opening dimension of 70 mm. In the case of an oval, there is no problem even if the major axis exceeds 70 mm.
このようにして溶鋼系スラグから回収した磁選屑を、転炉の炉上に設置される、ホッパー、原料切り出し装置、秤量機、シュートなどから構成される慣用の副原料投入設備に巻き上げて収容し、溶銑の脱炭精錬において、原料切り出し装置及び秤量機を用いて収容した磁選屑を任意の量、任意の時期に切り出し、冷却材として転炉炉上から転炉内に投入する。 In this way, the magnetic separation scrap recovered from the molten steel slag is wound up and stored in a conventional auxiliary raw material charging facility that is installed on the converter furnace and is composed of a hopper, a raw material cutting device, a weighing machine, a chute, and the like. In the decarburization and refining of hot metal, the magnetically separated scrap accommodated using a raw material cutting device and a weighing machine is cut in an arbitrary amount and at an arbitrary time, and is put into the converter from the converter as a coolant.
冷却材として使用する磁選屑は、溶鋼系スラグから回収した磁選屑であるので、磁選屑を構成する地金及びスラグの燐及び硫黄の含有量がともに少なく、溶製される溶鋼の燐のピックアップ及び硫黄のピックアップを懸念することなく使用することができる。また、溶鋼系スラグから回収した磁選屑では、地金の炭素濃度が低く、融点が高くなるが、溶銑の転炉脱炭精錬では１６００℃以上の温度となるので容易に溶解する。 Since the magnetic separation waste used as the coolant is the magnetic separation waste recovered from the molten steel slag, the contents of both the metal and the slag phosphorus and sulfur constituting the magnetic separation waste are small, and the molten steel phosphorus pick-up to be melted is produced. And sulfur pickup can be used without concern. In the magnetic separation scrap recovered from the molten steel slag, the carbon concentration of the bare metal is low and the melting point is high. However, in the hot metal converter decarburization refining, the temperature becomes 1600 ° C. or higher, so that it easily melts.
図１は、溶鋼系スラグから回収した磁選屑（「溶鋼系磁選屑」と呼ぶ）、溶銑系スラグから回収した磁選屑（「溶銑系磁選屑」と呼ぶ）、及び、軽量鉄スクラップを、溶銑の脱炭精錬に投入したときの溶鋼中の硫黄濃度の上昇量を調査した結果を示す図である。また、図２は、同様に、溶鋼系磁選屑、溶銑系磁選屑、及び、軽量鉄スクラップを投入したときの溶鋼中の燐濃度の上昇量を調査した結果を示す図である。図１及び図２に示すように、溶鋼系磁選屑を使用した場合には、投入量の多い少ないに拘わらず、硫黄及び燐のピックアップを防止することができる。これに対して、溶銑系磁選屑を使用した場合には、燐及び硫黄のピックアップが発生する。 FIG. 1 shows a magnetic separation scrap recovered from molten steel slag (referred to as “molten magnetic separation waste”), a magnetic separation scrap recovered from molten iron slag (referred to as “molten magnetic separation waste”), and lightweight iron scrap. It is a figure which shows the result of having investigated the raise amount of the sulfur density | concentration in molten steel when throwing into the decarburization refining of this. Moreover, FIG. 2 is a figure which similarly shows the result of having investigated the raise amount of the phosphorus density | concentration in molten steel when molten steel type | system | group magnetic sorting waste, hot metal type | system | group magnetic sorting scrap, and a lightweight iron scrap are thrown in. As shown in FIGS. 1 and 2, when molten steel-based magnetic separation is used, it is possible to prevent the pickup of sulfur and phosphorus regardless of the large amount of input. On the other hand, when hot metal magnetic separation is used, pick-up of phosphorus and sulfur occurs.
従来、冷却材として主に使用されている鉄鉱石などの酸化鉄系冷却材に比較して、溶鋼系磁選屑は酸化鉄を殆ど含有していないので、酸化鉄の還元に費やされる熱量は酸化鉄系冷却材に比較して極めて少ない。つまり、溶鋼系磁選屑の冷却能は顕熱及び潜熱のみに依存し、顕熱、潜熱及び還元熱を冷却能として有する鉄鉱石などの酸化鉄系冷却材の冷却能の１／３〜１／２になる（鉄鋼便覧第II巻製銑・製鋼（日本鉄鋼協会編、第３版、４７６頁）参照）。実際、本発明等の試験結果でも、図３に示すように、溶鋼系磁選屑の冷却効果は、鉄鉱石の冷却効果の１／３〜１／２であった。従って、同じ冷却効果を得る場合には、酸化鉄系冷却材に比べて２〜３倍の使用量を必要とする。換言すれば、酸化鉄系冷却材の場合には少ない添加量であっても溶鋼温度は大きく変化するが、つまり、過剰或いは過小の場合には溶鋼温度が大きく変化するが、溶鋼系磁選屑の場合には溶鋼温度の変化量が少なく、その分、溶鋼温度を精度良く調整することができる。 Compared to iron oxide-based coolants such as iron ore that have been used mainly as coolants, molten steel-based magnetic separation scraps contain almost no iron oxide, so the amount of heat consumed to reduce iron oxide is oxidized. Very little compared to ferrous coolant. In other words, the cooling capacity of the molten steel magnetic separation depends only on sensible heat and latent heat, and 1/3 to 1 / 2 (Refer to Steel Handbook, Volume II Steelmaking and Steelmaking (Japan Iron and Steel Institute, 3rd edition, page 476)). Actually, even in the test results of the present invention, as shown in FIG. 3, the cooling effect of the molten steel-based magnetic separation was 1/3 to 1/2 of the cooling effect of iron ore. Therefore, in order to obtain the same cooling effect, the amount used is 2 to 3 times that of the iron oxide-based coolant. In other words, in the case of an iron oxide-based coolant, the molten steel temperature changes greatly even with a small addition amount, that is, when the amount is excessive or too small, the molten steel temperature changes greatly. In this case, the amount of change in the molten steel temperature is small, and accordingly, the molten steel temperature can be adjusted with high accuracy.
また、酸化鉄分を含有していないので、酸化鉄と溶銑中炭素との反応によるＣＯガスの発生がなく、更に、添加時、溶鋼系磁選屑自体がスラグにガス抜けの通路となる孔を空けるので、これによるスラグのフォーミング抑制効果も加わり、スラグのフォーミングを抑制することができる。また更に、密度が大きいことから溶融スラグ中に埋没し、溶銑或いは溶鋼の温度変化が迅速に現われ、温度調整の精度を高めることができる。 In addition, since it does not contain iron oxide, there is no generation of CO gas due to the reaction of iron oxide and carbon in the hot metal, and when added, the molten steel-based magnetic separation scrap itself pierces the slag as a gas escape passage. Therefore, the effect of suppressing slag forming is also added, and slag forming can be suppressed. Furthermore, since the density is high, it is buried in the molten slag, and the temperature change of the hot metal or molten steel appears rapidly, and the accuracy of temperature adjustment can be increased.
溶鋼系磁選屑を冷却材として使用する場合、脱炭精錬のどの時点であっても構わないが、溶鋼系磁選屑は酸化鉄分をほとんど含有せず、溶銑中或いは溶鋼中の炭素と反応しないので、酸化鉄系冷却材を使用した場合に比べて精錬反応の制御、つまり溶鋼中炭素濃度の調整が容易になる。この点から、溶鋼系磁選屑は、溶鋼中の炭素濃度の調整が行われる脱炭精錬の中期から末期における冷却剤として使用することが好ましい。脱炭精錬の初期には従来の酸化鉄系冷却材などを使用してもよい。 When using molten steel-based magnetic separation as a coolant, it may be at any point in the decarburization refining process, but the molten steel-based magnetic separation does not contain iron oxide and does not react with carbon in the hot metal or molten steel. Compared with the case where an iron oxide-based coolant is used, control of the refining reaction, that is, adjustment of the carbon concentration in the molten steel becomes easier. From this point, it is preferable to use the molten steel magnetic separation scrap as a coolant in the middle to the end of decarburization refining in which the carbon concentration in the molten steel is adjusted. In the initial stage of decarburization refining, a conventional iron oxide-based coolant may be used.
このように、本発明では溶鋼系磁選屑のみを転炉脱炭精錬の冷却材として使用するので、溶鋼系磁選屑の使用量を制限しなくても、また、生石灰などの造滓剤の使用量を増やさなくても、溶鋼中の燐濃度及び硫黄濃度の上昇を起こすことなく、脱炭精錬終了時の溶鋼の温度を所望する温度範囲に調整することができる。 As described above, in the present invention, only the molten steel-based magnetic separation waste is used as a coolant for converter decarburization refining, so even if the amount of molten steel-based magnetic separation waste is not limited, the use of a fossilizing agent such as quick lime is also used. Even if the amount is not increased, the temperature of the molten steel at the end of decarburization refining can be adjusted to a desired temperature range without causing an increase in phosphorus concentration and sulfur concentration in the molten steel.
上吹きランスから酸素ガスを吹き付け、底吹き羽口から攪拌用ガスを吹き込む転炉における本発明の実施例を説明する。図４に、上吹きランスからの送酸速度、媒溶材（生石灰）の投入時期、冷却材としての鉄鉱石の投入時期、及び、冷却材としての溶鋼系磁選屑の投入時期を合わせて示す。横軸は、１ヒートの処理時間を百分率で示したものである。 An embodiment of the present invention in a converter in which oxygen gas is blown from the top blowing lance and stirring gas is blown from the bottom blowing tuyere will be described. FIG. 4 also shows the acid feed rate from the top blowing lance, the charging time of the solvent medium (quick lime), the charging time of the iron ore as the cooling material, and the charging time of the molten steel-based magnetic separation scrap as the cooling material. The horizontal axis shows the processing time for one heat in percentage.
図４に示すように、上吹きランスからの吹錬開始後、直ちに生石灰の投入を開始し、着火後排ガスが安定した時期から冷却材として鉄鉱石を連続投入した。鉄鉱石の投入が安定した吹錬２０〜３０％の吹錬中期の時点より、溶鋼系磁選屑の連続投入を開始した。連続投入の開始から終了まで、鉄鉱石と同様に１２００ｋｇ／分程度の投入速度で投入した。投入中、溶鋼系磁選屑は鉄酸化物を含有しないことからスラグのフォーミングも少ないため、送酸速度は変化なしとした。実際に溶鋼系磁選屑の投入中はスラグのフォーミングが認められなかった。 As shown in FIG. 4, immediately after the start of blowing from the top blowing lance, quick lime was started and iron ore was continuously supplied as a coolant from the time when the exhaust gas was stabilized after ignition. From the midpoint of 20-30% blowing, where iron ore was stably charged, continuous injection of molten steel-based magnetic separation was started. From the start to the end of continuous charging, charging was performed at a charging speed of about 1200 kg / min, similar to iron ore. During the charging, since the molten steel magnetic separation scrap does not contain iron oxide, there is little slag forming, so the acid feed rate was kept unchanged. In fact, slag forming was not observed during the introduction of molten steel magnetic separation.
その後、吹錬７５〜９０％の時点でサブランスを投入し、その時点での浴温度及び溶銑中炭素濃度を測定し、目標の温度及び炭素濃度に向けて必要酸素量及び必要冷却材量を推定した。そして、吹錬末期、溶鋼系磁選屑を目標温度への温度調整のための冷却材として使用した。投入速度は、投入完了後から脱炭精錬終了時まで３０秒以上の時間を確保するために、鉄鉱石の投入時と同様に、２４００ｋｇ／分程度として、最高３０００ｋｇ／分までを投入上限として連続投入を行った。 After that, when the blow smelting is 75-90%, the lance is introduced, the bath temperature and the carbon concentration in the hot metal at that time are measured, and the required oxygen amount and required coolant amount are estimated for the target temperature and carbon concentration. did. At the end of the blow smelting, molten steel-based magnetic separation was used as a coolant for adjusting the temperature to the target temperature. In order to secure a time of 30 seconds or more from the completion of decarburization to the end of decarburization refining, the charging speed is set to about 2400 kg / min and continuously up to a maximum of 3000 kg / min in the same manner as when iron ore is charged. The input was performed.
その結果、燐及び硫黄のピックアップの発生がなく、吹錬終点の溶鋼温度及び炭素濃度を所望する範囲に精度良く調整することができた。 As a result, there was no generation of phosphorus and sulfur pick-up, and the molten steel temperature and carbon concentration at the end of blowing were able to be accurately adjusted to the desired ranges.
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